CUDA 9.1 installation error: does not have a version.txt file! Ensure you are installing to an existing toolkit directory

You might be trying to install the "patch" instead of the main installer.

Is your file about 70 MB size instead of the more expected 1.7 GB size? If yes, then you are probably installing the "patch" first before the main installer.

I also tried installing the "patch" first and got an error and then I was confused. Then I realized I had the wrong filename and did an ls -alrth and got the filename for the larger 1.7 GB installer and tried that and now it is installing without the error message.

The files I downloaded were not clearly labeled to indicate what file was the installer and what was the main installer (the filenames are all cuda_${version}.run).